How to choose a caliper, micrometer or gauge
By Grant, Inspection Tool Specialists. Reviewed November 2026.
Three things decide which measuring tool you need: what you measure (external size, internal size, depth, step, gap or radius), the resolution and accuracy the job requires, and whether the readings must be recorded. Answer those first. The cheapest tool that meets the tolerance is usually the right one.
Which tool for which measurement?
| Measurement | Tool | Typical in our range |
|---|---|---|
| External size or length, general workshop | Digital or vernier caliper, 150 mm | Digital 150 mm, 0.01 mm; vernier 150 mm monoblock, 0.02 mm |
| Larger parts, high precision | Digital caliper, 300 mm | Digital 300 mm, 0.01 mm |
| Diameters to finer resolution | Micrometer | Micrometer |
| Internal bores | Conical taper bore gauge set | Conical taper bore gauge set |
| Gaps and clearances | Feeler gauge set | Metric feeler gauge set |
| Radii and curves | Radius gauge set | Radius gauge set, 4-piece |
| Comparing parts to a master, or height readings | Digital comparator or height comparator | EDC2000-B digital comparator; EHG12-01 digital height comparator |
Digital or vernier?
A digital caliper shows the reading at a glance and can send data to a record. A vernier caliper needs no battery and is simple and robust, but the reading is taken by eye. Our digital calipers are listed with an IP67 rating, which means they resist dust and water, so they suit workshops where a vernier would suffer.
Resolution and tolerance
A common rule is that the tool's resolution should be at least about a tenth of the tolerance you must check. A 0.02 mm vernier is enough for a 0.2 mm tolerance; a tolerance of 0.02 mm needs a finer tool and a stable environment.
Checking the tool
Check the tool against gauge blocks or a known reference before a batch of measurements, and keep the record. Calibrating your own tools is a separate service. Send us the list and we will confirm what we can offer.
Care
Store measuring tools clean and dry, and do not measure with damaged jaws or faces. A tool that has been dropped should be checked before further use.
Which tool should I buy?
Tell us the parts you measure, the tolerances, the resolution you need, whether readings must be recorded or sent to a system, and where the tool will be used. With that we can recommend a tool and provide pricing.
Price guide
As a guide to our current range, including VAT: feeler and radius gauge sets from about R340; micrometers from about R550; vernier calipers from about R920; digital calipers from about R1,880; bore gauge sets from about R2,560; digital comparators from about R9,900 to R43,700. Prices change, so check the product pages.